[Beginner] MATLAB : Error ??? Index exceeds matrix dimensions but I can't fix it

Hi all, I'm just a beginner in Matlab and I need help about an issue in my program. When I try to run my program, I have one of the following error : ??? Index exceeds matrix dimensions in those lines :

Error in ==> reseau_capteur_def at 70 mesg_decod(3,:)=xor(xor(zb_gt(7,:),zb_gt(2,:)),zb_gt(4,:));

Error in ==> reseau_capteur_def at 74 mesg_decod(4,:)=xor(xor(zb_gt(7,:),zb_gt(2,:)),zb_gt(3,:));

Error in ==> reseau_capteur_def at 65 mesg_decod(2,:)=xor(xor(zb_gt(7,:),zb_gt(3,:)),zb_gt(4,:));

Can you help me to solve this please? Because I'm still a beginner in Matlab and I spent a whole week trying to solve this but with no success, and thank you in advance for your help.

Here's a part of the program where the error occurs (and the whole program if attached to this message):

 % on réencode en utilisant le codage 
      y_trans(1,:)=xor(zdec_rel(1,:),zdec_rel(2,:));
      y_trans(2,:)=xor(xor(zdec_rel(1,:),zdec_rel(3,:)),zdec_rel(4,:));
      y_trans=2*y_trans-1;
      %signal reçu à la gateway depuis le relais
      for ii=1:2
         z_gt(ii,:)=awgncomplex(1,length_msg,SNR(1,m),HH_rel_gt*y_trans(ii,:));
      end
      % On égalise les signaux au niveau de la gateway
      for ii=1:N_capteurs
         zz_gt(ii,:)=conj(HH_sens_gt(1,ii))*y_gt(ii,:)/(abs(HH_sens_gt(1,ii)))^2;
      end
      for ii=1:2
         za_gt(ii,:)=conj(HH_rel_gt)*z_gt(ii,:)/(abs(HH_rel_gt))^2;
      end
      zb_gt=[0.5*(sign(real(zz_gt))+1);0.5*(sign(real(za_gt))+1)];   
      zb_gt(out_pk(1,1),:)=zeros(1,length_msg);
      zb_gt(out_pk(1,2),:)=zeros(1,length_msg);
      %zb_gt
      % L'algorithme de décodage commence ici, on distingue les différents cas
      if ((out_pk(1,1)==1) & (out_pk(1,2)==2))
         mesg_decod(1,:)=xor(xor(zb_gt(6,:),zb_gt(3,:)),zb_gt(4,:));
         mesg_decod(2,:)=xor(xor(zb_gt(7,:),zb_gt(3,:)),zb_gt(4,:));
         mesg_decod(3,:)=zb_gt(3,:);
         mesg_decod(4,:)=zb_gt(4,:);
      elseif ((out_pk(1,1)==1) & (out_pk(1,2)==3))
         mesg_decod(1,:)=xor(xor(zb_gt(5,:),zb_gt(2,:)),zb_gt(4,:));
         mesg_decod(3,:)=xor(xor(zb_gt(7,:),zb_gt(2,:)),zb_gt(4,:));
         mesg_decod(2,:)=zb_gt(2,:);
         mesg_decod(4,:)=zb_gt(4,:);
      elseif ((out_pk(1,1)==1) & (out_pk(1,2)==4))
         mesg_decod(4,:)=xor(xor(zb_gt(7,:),zb_gt(2,:)),zb_gt(3,:));
         mesg_decod(1,:)=xor(xor(zb_gt(5,:),zb_gt(2,:)),mesg_decod(4,:));
         mesg_decod(2,:)=zb_gt(2,:);
         mesg_decod(3,:)=zb_gt(3,:);
      elseif ((out_pk(1,1)==2) & (out_pk(1,2)==3))
         mesg_decod(2,:)=xor(xor(zb_gt(5,:),zb_gt(1,:)),zb_gt(4,:));
         mesg_decod(3,:)=xor(xor(zb_gt(6,:),zb_gt(1,:)),zb_gt(4,:));
         mesg_decod(1,:)=zb_gt(1,:);
         mesg_decod(4,:)=zb_gt(4,:);
      elseif ((out_pk(1,1)==2) & (out_pk(1,2)==4))
         mesg_decod(4,:)=xor(xor(zb_gt(6,:),zb_gt(1,:)),zb_gt(3,:));
         mesg_decod(2,:)=xor(xor(zb_gt(5,:),zb_gt(1,:)),mesg_decod(4,:));
         mesg_decod(1,:)=zb_gt(1,:);
         mesg_decod(3,:)=zb_gt(3,:);
      else 
         mesg_decod(4,:)=xor(xor(zb_gt(5,:),zb_gt(1,:)),zb_gt(2,:));
         mesg_decod(3,:)=xor(xor(zb_gt(6,:),zb_gt(1,:)),mesg_decod(4,:));
         mesg_decod(1,:)=zb_gt(1,:);
         mesg_decod(2,:)=zb_gt(2,:);
      end

Answer 1

[Thorsten]

What does

size(zb_gt)

return before those lines? Presumably it has to few rows.

[Yassine Bouchdoug]

Hi and thank you for your answer,

When I try to do the size(zb_gt) it gives me (7 lines 200 columns) : ans =

     7   200

You can find the whole program (with the instructions before those on the message) attached to the message, do not hesitate to look it up for a better understanding of it (and don't worry it's not a very long program :) ).